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Title: Atypical Hydrogen Uptake on Chemically Activated, Ultramicroporous Carbon

Abstract

Hydrogen adsorption at near-ambient temperatures on ultramicroporous carbon (UMC), derived through secondary chemical activation from a wood-based activated carbon was studied using volumetric and gravimetric methods. The results showed that physisorption is accompanied by a process of different nature that causes slow uptake at high pressures and hysteresis on desorption. In combination, this results in unusually high levels of hydrogen uptake at near-ambient temperatures and pressures (e.g. up to 0.8 wt % at 25 oC and 2 MPa). The heat of adsorption corresponding to the slow process leading to high uptake (17 20 kJ/mol) is higher than usually reported for carbon materials, but the adsorption kinetics is slow, and the isotherms exhibit pronounced hysteresis. These unusual properties were attributed to contributions from polarization-enhanced physisorption caused by traces of alkali metals residual from chemical activation. The results support the hypothesis that polarization-induced physisorption in high surface area carbons modified with traces of alkali metal ions is an alternate route for increasing the hydrogen storage capacity of carbon adsorbents.

Authors:
 [1];  [1];  [1];  [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); High Temperature Materials Laboratory
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
979242
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Carbon; Journal Volume: 48; Journal Issue: 5
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; ACTIVATED CARBON; ADSORBENTS; ADSORPTION; ADSORPTION HEAT; ALKALI METALS; CAPACITY; CARBON; CHEMICAL ACTIVATION; DESORPTION; HYDROGEN; HYDROGEN STORAGE; HYPOTHESIS; HYSTERESIS; ISOTHERMS; KINETICS; SURFACE AREA

Citation Formats

Bhat, Vinay V, Contescu, Cristian I, Gallego, Nidia C, and Baker, Frederick S. Atypical Hydrogen Uptake on Chemically Activated, Ultramicroporous Carbon. United States: N. p., 2010. Web. doi:10.1016/j.carbon.2009.12.001.
Bhat, Vinay V, Contescu, Cristian I, Gallego, Nidia C, & Baker, Frederick S. Atypical Hydrogen Uptake on Chemically Activated, Ultramicroporous Carbon. United States. doi:10.1016/j.carbon.2009.12.001.
Bhat, Vinay V, Contescu, Cristian I, Gallego, Nidia C, and Baker, Frederick S. Fri . "Atypical Hydrogen Uptake on Chemically Activated, Ultramicroporous Carbon". United States. doi:10.1016/j.carbon.2009.12.001.
@article{osti_979242,
title = {Atypical Hydrogen Uptake on Chemically Activated, Ultramicroporous Carbon},
author = {Bhat, Vinay V and Contescu, Cristian I and Gallego, Nidia C and Baker, Frederick S},
abstractNote = {Hydrogen adsorption at near-ambient temperatures on ultramicroporous carbon (UMC), derived through secondary chemical activation from a wood-based activated carbon was studied using volumetric and gravimetric methods. The results showed that physisorption is accompanied by a process of different nature that causes slow uptake at high pressures and hysteresis on desorption. In combination, this results in unusually high levels of hydrogen uptake at near-ambient temperatures and pressures (e.g. up to 0.8 wt % at 25 oC and 2 MPa). The heat of adsorption corresponding to the slow process leading to high uptake (17 20 kJ/mol) is higher than usually reported for carbon materials, but the adsorption kinetics is slow, and the isotherms exhibit pronounced hysteresis. These unusual properties were attributed to contributions from polarization-enhanced physisorption caused by traces of alkali metals residual from chemical activation. The results support the hypothesis that polarization-induced physisorption in high surface area carbons modified with traces of alkali metal ions is an alternate route for increasing the hydrogen storage capacity of carbon adsorbents.},
doi = {10.1016/j.carbon.2009.12.001},
journal = {Carbon},
number = 5,
volume = 48,
place = {United States},
year = {Fri Jan 01 00:00:00 EST 2010},
month = {Fri Jan 01 00:00:00 EST 2010}
}
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